Nozzle flows of dense gases

Abstract

Numerical solutions for steady inviscid flows in conventional converging–diverging nozzles are obtained. The fluids considered are Bethe–Zel’dovich–Thompson fluids, i.e., those having specific heats so large that the fundamental derivative of gas dynamics is negative over a finite range of pressures and temperatures. Three general classes of flow are delineated which include two nonclassical types in addition to the usual classical flows; the latter are qualitatively similar to those of perfect gases. The nonclassical flows are characterized by isentropes containing as many as three sonic points. Numerical solutions depicting finite-strength expansion shocks, steady flows with shock waves standing upstream of the nozzle throat, and steady flows containing as many as three shock waves are presented. Flows having arbitrarily large-exit Mach numbers are found to be possible only if a sonic expansion shock is formed in the nozzle. This observation contrasts with prediction based on the perfect gas theory which states that the occurrence of shock waves always results in a subsonic exit flow.